1. Field of the Invention
The present invention relates to a slider, a head, a head device and a read/write apparatus.
2. Discussion of Background
In a read/write apparatus that is employed as an external writing apparatus for a computer, a flying type head that generates a lift force at the slider to cause it to fly over a disk-like medium by applying the principle of dynamic air pressure is employed. In this type of read/write apparatus, the slider is in contact with the disk-like medium when the disk-like medium is in a stopped state and when the disk-like medium rotates, air flow generated by the rotation acts on the air bearing surface of the slider to cause it to fly over the disk-like medium while maintaining a specific flying height to perform read/write of information. Typical read/write apparatuses used to date are magnetic read/write apparatuses in which a magnetic disk and a magnetic head having a slider are employed. Japanese Examined Patent Publication No. 569/1982 and U.S. Pat. No. 3,823,416 disclose taper flat type sliders.
One of the essential requirements that a read/write apparatus must satisfy to achieve high density writing is a reduction in the flying height. In recent years, high density writing performed by read/write apparatuses has necessitated a reduction in the flying height at a portion of the slider where the transducer is provided down to 25 nm or less. In addition, when adopting zone bit writing, whereby writing is performed at the maximum writing density over the entire surface of the disk-like medium, it is desirable that the flying height be as consistent as possible over the entire seek area from the inner track to the outer track of the disk-like medium.
In addition, as a means for achieving a larger storage capacity in a magnetic storage device, a head which employs a magnetoresistive element (hereafter referred to as an MR element) as a read element has been proposed and put into practical use. Unlike in an inductive transducer of the prior art whose signal output is dependent upon the circumferential speed of the disk-like medium, the signal output in an MR element is not dependent upon the circumferential speed of the disk-like medium. As a result, in a head employing an MR element as a read element, a read signal which is not dependent upon the circumferential speed of the disk-like medium is achieved. The air bearing surface of a head must be designed to ensure that an almost constant flying height is achieved over the entire writing area of the disk-like medium.
Next, due to the structural features of a head, the transducers are located approximately 35 to 50 .mu.m further inward from the trailing edge. When causing a head structured as described above to fly at an extremely small flying height of 25 nm or less, it is necessary to set an attitude angle (pitch angle) in the direction of the length of the slider during flight smaller than 3.times.10.sup.-4 (rad) as a means for preventing contact between the trailing edge of the slider and the disk-like medium. While Japanese Pat. No. 2,573,236 discloses a technology whereby the flying state is stabilized in a range over which the pitch angle is small, it is difficult to maintain a consistent flying height from the inner track to the outer track so that the flying height remains at 25 nm or less since the head disclosed in this patent is a taper flat type head, which, in turn, makes it difficult to prevent problems such as a head crash that occurs when the trailing edge of the slider comes in contact with the disk-like medium.
As a means for achieving a constant flying height, designing a slider as a negative pressure slider that utilizes negative pressure has been considered. Such sliders are disclosed in Japanese Examined Patent Publication No. 1619/1995 and U.S. Pat. No. 4,734,803. However, there are problems with this type of slider, such as dust present inside the magnetic storage device becoming adhered to the indented portion of the negative pressure slider, greatly changing the flying height of the slider and the slider attracting to the surface of the disk-like medium. Thus, in order to put a negative pressure slider into practical use, a slider having a new flying surface that prevents dust from affecting its operation, good flying start characteristics (takeoff characteristics) and in which the attracting phenomenon is avoided, must be developed. Problems caused by dust in the magnetic storage device adhering to the slider are not limited to a negative pressure slider and can occur in other types of sliders as well.
Another crucial requirement is an improvement in the following stability of the slider relative to oscillations of the disk. An air lubricating film formed between the slider and the disk-like medium has a cushioning effect and the slider flies while maintaining a balance between the air lubricating film and the recovering force of the head suspension. When the oscillation frequency of the disk-like medium increases, the following stability of the slider deteriorate due to the inertia of the slider mass. In order to design a slider with good following stability, it is crucial to achieve a high level of air lubricating film stiffness.
Since it is extremely difficult to satisfy the technical objectives and requirements described above with a head or a slider in the prior art, development of a new head is required. Furthermore, an optical disk apparatus which utilizes a near-field read/write system has come to light in recent years since it can break through the limitation of high writing density achieved by magnetic read/write apparatuses. In the optical disk apparatus utilizing a near-field writing and reading system, a flying type slider is employed. Consequently, the same problems explained with relation to the magnetic read/write apparatuses exist and must be addressed.